Many municipalities may now enforce quite close tolerances in road construction that require the installed manhole frame once mounted onto the annular concrete manhole spacer ring, to be substantially flush with the roadway surface, that is, the surface of the asphalt. For example, in applicant's experience, at least one municipality requires that the manhole frame be parallel to the asphalt surface and offset from the asphalt surface no more than seven millimetres.
Because the manhole apertures themselves are horizontal, and often the road grade is not horizontal, for example having a grade of up to four percent, or in extreme cases a twelve percent grade and/or a seven percent crossfall, it is conventional that, firstly, an annular concrete spacer ring, sometimes referred to as a “donut” or a “riser”, is installed onto the manhole aperture, and then a manhole frame is mounted on top of the concrete spacer ring. Because the manhole frame is very heavy, being constructed of solid metal such as grey or ductile iron, it is often a two-man lift to set the manhole frame onto the concrete spacer ring and then a two-man job to adjust the tilt or incline of the manhole frame on top of the concrete spacer ring. Typically what is done is one man lifts one side or edge of the manhole frame while the second man inserts makeshift shims, including whatever small pieces of wood or rocks may be at hand, so as to adjust the angular relation of the manhole frame onto the horizontal upper surface of the concrete spacer ring. In this fashion, the manhole frame is adjusted both vertically and tilted relative to the concrete spacer ring so as to bring the upper surface of the manhole frame within the specified tolerances of the anticipated upper surface of the asphalt.
Once a manhole frame has been so adjusted, the roadway construction continues around the manhole frame, for example, as the crush is compacted. This may result in the manhole frame being disturbed before the concrete spacer ring and manhole frame are encased in concrete so as to leave the manhole frame out of adjustment because of disruption to the shims. This then means that the manhole frame must again be adjusted either before or after the asphalt is laid. Thus, as may be seen, the prior art method of adjusting the manhole frame is both labour intensive and prone to later misalignment requiring the adjustment work to be redone.
Therefore there exists a need in the prior art for a simple to install, easily adjustable mechanism for adjusting the vertical height of a manhole frame above the concrete spacer ring and for adjusting the angular inclination of the manhole frame relative to the concrete spacer ring.